1. Field of the Invention
This invention relates to an optical head device, and in particular to an optical head device having a support shaft, an optical system holding member movably supported by the support shaft, an optical system held by the optical system holding member, and drive means for moving the optical system. Such an optical head device is used to record or reproduce information on or from a recording carrier in an optical information recording-reproducing apparatus, such as an optical disk memory.
2. Related Background Art
In an optical head device according to the prior art, a driving mechanism for an optical system such as an objective has been made separately from an optical head body containing a light source, for instance, therein and the final apparatus has been constructed by joining these. An example of this will hereinafter be described.
FIG. 1 of the accompanying drawings is a perspective view showing only the objective driving portion in the optical head device according to the prior art. As shown in FIG. 1, an objective holding member 28 is inserted over a support shaft 26 secured to a base bed 21 as by being pressed in, through a bearing, and an objective 23 and a weight 29 substantially equal in weight to the objective 23 are mounted near the support shaft 26. A neutral point retaining member, not shown, is mounted below the weight 29. A coil 24 for focusing is wound on the outer peripheral portion of the objective holding member 28, and a coil 25b for tracking and a coil 25a for tracking (not shown, is disposed at a location opposite to the coil 25b for tracking with respect to the support shaft 26) are mounted on the coil 24. Permanent magnets 27a and 27b for focusing having their opposed poles formed near the outer and inner peripheral portions of the objective holding member 28 are secured to the base bed 21 so as to be opposed to the coil 24 for focusing, and permanent magnets 22aand 22b tracking are secured in the vicinity of the outer peripheral portion of the objective holding member 28 so as to be opposed to the coils 25a and 25b for tracking. By an electromagnetic force produced by a current flowing to the coil 24 for focusing and the coils 25a and 25b for tracking and magnetic fields formed relative to the respective coils, the objective holding member 28 is vertically moved and horizontally pivoted about the support shaft 26.
The optical head device has been constructed by securing the base bed 21 to which the permanent magnets 22a, 22b for tracking, the permanent magnets 27a, 27b for focusing and the support shaft 26 are secured, to the optical head body by means of screws.
However, in the prior-art optical head device described above, the base bed, screws, etc. have been required. This has led to a great number of parts and has required much time for assembly. Moreover, it is difficult to make the optical head device light in weight. Also, the mounting of the support shaft 26 with respect to the optical head body is done through the intermediary of the base bed 21. This reduce the accuracy of the inclination of the support shaft 26 with respect to the optic axis of the light beam from the optical head body